title: Impaired allergy diagnostics among parasite-infected patients caused by IgE antibodies to the carbohydrate epitope galactose-α 1,3-galactose.
abstract: BACKGROUND
  The carbohydrate epitope galactose-α 1,3-galactose (α-Gal) is abundantly expressed on nonprimate mammalian proteins. We have recently shown that α-Gal is responsible for the IgE binding to cat IgA, a newly identified cat allergen (Fel d 5).
  
  
  OBJECTIVE
  We sought to investigate the diagnostic relevance of IgE antibodies to Fel d 5 and α-Gal among parasite-infected patients from central Africa without cat allergy compared with patients with cat allergy from the same region.
  
  
  METHODS
  Sera from 47 parasite-infected patients and 31 patients with cat allergy were analyzed for total IgE and IgE antibodies against cat dander extract (CDE) by using the ImmunoCAP system. Inhibition assay was performed with α-Gal on solid phase-bound CDE. The presence of IgE specific for the major cat allergen Fel d 1, Fel d 5, and α-Gal was analyzed by means of ELISA.
  
  
  RESULTS
  Among the 47 parasite-infected patients, 85% had IgE antibodies against α-Gal (OD; median, 0.175; range, 0.102-1.466) and 66% against Fel d 5 (OD; median, 0.13; range, 0.103-1.285). Twenty-four of the parasite-infected patients were sensitized to CDE, and 21 of them had IgE antibodies to Fel d 5 and α-Gal. There was no correlation between IgE levels to CDE and rFel d 1 among the parasite-infected patients but a strong correlation between CDE and Fel d 5 and α-Gal (P < .001). Among the group with cat allergy, only 5 patients had IgE to α-Gal, and nearly 75% (n = 23) had IgE to rFel d 1 (median, 7.07 kU(A)/L; range, 0.51-148.5 kU(A)/L). In contrast, among the patients with cat allergy, there was a correlation between IgE levels to CDE and rFel d 1 (P < .05) but no correlation between CDE and Fel d 5 and α-Gal.
  
  
  CONCLUSIONS
  IgE to α-Gal causes impaired allergy diagnostics in parasite-infected patients. Screening for IgE to rFel d 1 and other allergens without carbohydrates might identify patients with true cat sensitization/allergy in parasite-infested areas.
authors.affiliation: Department of Medicine, Clinical Immunology and Allergy Unit, Karolinska Institutet and University Hospital, Stockholm, Sweden.
authors.forename: Kurt
authors.initials: K
authors.lastname: Arkestål
authors.forename: Elopy
authors.initials: E
authors.lastname: Sibanda
authors.forename: Cecilia
authors.initials: C
authors.lastname: Thors
authors.forename: Marita
authors.initials: M
authors.lastname: Troye-Blomberg
authors.forename: Takafira
authors.initials: T
authors.lastname: Mduluza
authors.forename: Rudolf
authors.initials: R
authors.lastname: Valenta
authors.forename: Hans
authors.initials: H
authors.lastname: Grönlund
authors.forename: Marianne
authors.initials: M
authors.lastname: van Hage
mesh_terms: D000818:Animals; D002241:Carbohydrates / Q000276:immunology; D002415:Cats; D003429:Cross Reactions; D004187:Disaccharides / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D000939:Epitopes / Q000276:immunology; D006023:Glycoproteins / Q000276:immunology*; D006373:Helminthiasis / Q000276:immunology*; D006801:Humans; D006967:Hypersensitivity / Q000097:blood / Q000175:diagnosis* / Q000276:immunology; D007073:Immunoglobulin E / Q000097:blood
chemical_list: D002241:Carbohydrates; D004187:Disaccharides; D000939:Epitopes; D006023:Glycoproteins; C055075:galactosyl-(1-3)galactose; D007073:Immunoglobulin E; C059296:Fel d 1 protein, Felis domesticus